This application describes a request for an advanced multi-photon laser upgrade for an existing microscope system currently housed at the VA Boston Healthcare System (VABHS) Jamaica Plain campus. The present application describes our need for this instrument, its technical specifications, examples of how research can be furthered at VABHS through the use of this instrument, and a plan for its administration. An important frontier in neuroscience research, which remains largely unexplored, is the understanding of how neuronal units function in complex neural circuits and how the function of these circuits is disrupted in disease states. The ability to dissect neural circuit function has expanded exponentially over the last decade. Particularly the advent of chronic multi- photon imaging and optogenetics opened up a window for probing causal relationships between different cell types (or other circuit components) and neural circuit function in vivo. Chronic time lapse imaging of the structure and function of circuit elements in vivo allows us to probe how circuit malfunction evolves over time in disease states and how to modulate it. This has potentially important implications for understanding the pathophysiology of several disorders that affect neural circuit function, including Stroke, Alzheimer's, Epilepsy, Autism, traumatic brain injury, PTSD and Sleep. An instrument with this ability does not currently exist in the Boston VA system. We have a unique opportunity with the acquisition of this instrument to transform research at VABHS, Finally, having this instrument on site will allow us to attract and retain the best possible scientific talent within our research service.